Will the real Roethke please stand up!

"Which I is I?" Theodore Roethke "In a Dark Time" on page 27.With the history that is stated in the introduction to the section on Roethke, it leads me to believe that this poem was mentioning his disorder. Having had people in my life that were manic depressive and others with schizophrenia, I can understand this poem in a way. It seems to me that he is talking about be in and out of touch with reality. The line "Which I is I" makes me believe this the most. I have heard many times that when a person with a mental disorder goes in and out of episodes, they can feel like they do not know themselves anymore. It seems to me that Roethke could have very well felt this way and this poem was expressing that.